What insights into age-related changes in skeletal muscle are provided by animal models?

This review addresses the following questions: (a) How do the age-related changes in muscle of animal models compare to those found in human muscle?, and (b) How do the changes characteristic of models for reduced or altered muscle use compare to the age-related changes in muscle? Regarding the first question, the vast majority of relevant animal research has focused on the rodents, and the age-related changes in rodent muscle are in many respects reminiscent of human aging. A possible difference is the existence of a more profound hypoplasia in human muscle. Research into the age-related changes in muscle in other species is extremely scarce. Regarding the second question, various experimental conditions of reduced or altered muscle use (e.g., denervation, limb immobilization, hindlimb suspension) offer valuable insight not because they exactly mimic normal aging; rather, they demonstrate the multifactorial nature of processes leading to muscle atrophy.